Conventionally, display devices, such as standard televisions and computer monitors, have a 4:3 aspect ratio. The aspect ratio is the ratio between width of the display or imaging device vs. height of the display or imaging device. For example, if an image being displayed on a standard display device has a width of four inches and a height of three inches, the displayed image would have an aspect ratio of 4:3.
Since the standard aspect ratio for display devices, such as televisions and computer monitors, is 4:3, most typical imaging devices also have an aspect ratio of 4:3 to facilitate easy viewing of the imaged object or scene. However, in many applications, such as filming, automotive electronic mirroring, surveillance, or security monitoring, it is desirable to image at a non-standard aspect ratio or wide aspect ratio, wherein a wide aspect ratio image is a species of a non-standard aspect ratio image, so as to maximize the field of view for the corresponding imager.
The field of view is defined, as illustrated in FIG. 16, as the angle θ related to a dimension of an imager 25. For example, if the imager 25 has a vertical dimension of I1, the corresponding field of view would be θ1. On the other hand, as illustrated by FIG. 16, if the imager 25 has a vertical dimension of I2, the corresponding field of view would be θ2. The field of view, θ, is determined by the following equation: tan(θ/2)=I/2f, wherein I is defined as a dimension of the imager (horizontal or vertical) and f is the focal length of the imager. Thus, as the dimension (I) of the imager 25 increases, the field of view (θ) increases and, as illustrated by FIG. 16, more of the image 35 can be captured by the imager 25.
The film industry for many years has imaged at wider aspect ratios, such as 2.35:1 and 1.81:1, so as to provide a better viewing at theaters. Moreover, it has been desirable for various industries to have wider aspect ratio imagers as part of their systems to provide a more comprehensive captured image without image loss. For example, the automotive industry has desired a wider aspect ratio imager for vehicles to provide a driver with a better view of objects around the vehicle. The surveillance industry also has desired a wider aspect ratio imager to provide a wider and more precise view of the area being monitored without using noisy or failure prone mechanically panning imagers.
However, these wider imaging aspect ratios can cause a problem when trying to display the wider aspect ratio image directly on a standard display device having the standard aspect ratio of 4:3.
Conventionally, a standard display device is setup to accept the analog equivalent of 720 pixels/row if the pixels are rectangular, or 640 pixels/row when dealing with square pixels. Typical NTSC encoders are designed to work in either rectangular or square pixel mode, and can therefore accept either 720 or 640 pixels/row.
However, when imaging at a wider aspect ratio, the image will typically have more than 720 pixels/row if the pixels are rectangular, or more than 640 pixels/row when dealing with square pixels. Therefore, a typical NTSC encoder or standard display device cannot accept such image data directly and be able to display it in a meaningful manner. To address this problem, broadcast industry has developed various techniques for displaying non-standard aspect ratio images on standard aspect ratio display devices.
For example, one technique used to display non-standard aspect ratio images on standard aspect ratio display devices is letterboxing. Letterboxing is a method of displaying a non-standard aspect ratio image on a display at the image's original aspect ratio as illustrated in FIGS. 1 and 2. To letterbox a non-standard aspect ratio image 1 filled with objects 10, as illustrated in FIG. 1, the non-standard wide aspect ratio image 3 filled with objects 10, as illustrated in FIG. 2, is displayed over the entire width of the 4:3 aspect ratio display device 2 and black bars 4 are added to the top and bottom to achieve the correct aspect ratio. The larger the width of the non-standard aspect ratio image, the thicker the black bars must be; i.e., a 1.66:1 aspect ratio image would have very small black bars, compared to a 2.35:1 aspect ratio image being displayed on a 4:3 aspect ratio display. Even if a wide screen display device such as a 16:9 aspect ratio display, black bars would be needed, but the bars would be smaller than when using a 4:3 display device. Although letterboxing provides one way to display a non-standard aspect ratio image on a standard display device, the displayed image loses resolution and thus desired information within the image may not be properly displayed to be recognizable.
Another technique used to display non-standard aspect ratio images on standard aspect ratio display devices is “pan&scan.” “Pan&scan” takes a non-standard aspect ratio image 1 filled with objects 10 of FIG. 1 and displays the non-standard aspect ratio image on a standard display device 2, as illustrated in FIG. 3, wherein the non-standard aspect ratio image's original height is maintained, but only a portion of the width of the non-standard aspect ratio image is employed to produce the 4:3 aspect ratio of the standard display device 2. Although “pan&scan” provides one way to display a non-standard aspect ratio image on a standard display device, “pan&scan” loses information 5 off the side(s) of the original image and can sometimes be very deceiving due to this loss of information.
As noted above, the various techniques to display a non-standard aspect ratio image on a standard display device provide images with various problems. Thus, it is desirable to provide a display method for a non-standard aspect ratio image to be displayed on a standard aspect ratio display device without losing resolution or information from the original image. Moreover, it is desirable to provide the best display resolution and size on the non-standard aspect ratio image as it is displayed on a standard aspect ratio display device. Lastly, it is desirable to display the most pertinent information being captured by a non-standard aspect ratio imager on a standard aspect ratio display device in real-time.